The advent of color copiers and the tremendous improvements recently achieved in the visual quality of copies produced by such photocopiers has opened up a new area of major concern in the fight against the fraudulent duplication and counterfeiting of valuable documents.
The almost daily reported cases of fraudulently color copied admission tickets to major events, securities and high face value redeemable coupons are only a few examples of a very large problem.
The prior art provides a technology where the background of an original document is printed by a complex combination of multicolor screens where a statement such as VOID or COPY is "hidden" to the casual visual scrutiny and upon copying, the screens that carry the hidden words become more prominent and hence the latter become visible to reveal the copied nature of the document. It is important to note that the prior art relies on the "revelation" of "hidden" information. This has an inherent weakness which results from the obvious ease with which the "revealed" information can always be erased or inhibited through successive copying. As a matter of fact it is currently known in the printing trade that, while on the one hand the successful provision of a "Standard Register" prescribed background on the original is rather difficult, on the other hand the inhibition of the revealable messages on the copy is relatively easy.
As distinctly opposed to the above described situation, the present invention consists of placing on the original document, through any one of the presently known printing processes, background information which is visually perceptible and readable to a greater or a lesser degree, but which upon color copying will be washed away thus alarming the user by its absence.